Abstract
Background: Leucine zipper tumor suppressor 2 (LZTS2), an emerging tumor-suppressor, is attenuated in multiple cancers including prostate, lung and colon cancer. However, its expression and upstream regulatory mechanisms in triple negative breast cancer (TNBC) still remain unknown.Materials and methods: The expression of LZTS2 in TNBC and matched para-carcinoma tissues was detected with immunohistochemistry. The correlations between LZTS2 expression and clinicopathological parameters were analyzed. Kaplan-Meier analysis was performed to determine the prognostic role of LZTS2 for TNBC patients. CCK-8, wound healing and transwell assay were used to detect the effect of LZTS2 overexpression on the proliferation, migration and invasion ability, respectively. The bioinformation algorithms were used to reveal the potential upstream regulatory miRNA. Then, dual-luciferase reporter assay was performed to confirm the regulatory effect of the chosen miRNA on the expression of LZTS2. miR-9-5p inhibitor was used to determine the effect of miR-9-5p on the subcellular localization of β-catenin. Then, western blotting was performed to reveal the effect of miR-9-5p on EMT-related proteins in TNBC cells. Xenograft tumor model was established to reveal the effect of miR-9-5p on TNBC progression in vivo.Results: Low expression of LZTS2 was observed in 62 of 95 cases of TNBC tissue. Low expression of LZTS2 was correlated with poor postoperative DFS and OS of TNBC patients. LZTS2 could inhibit the proliferation, migration and invasion ability of TNBC cells. LZTS2 could be downregulated by miR-9-5p in TNBC, and the nuclear export of β-catenin was suppressed. Consequently, miR-9-5p inhibitor downregulated E-cadherin and upregulated N-cadherin, Twist and Vimentin in TNBC cells. Xenograft tumor model showed that miR-9-5p inhibitor could upregulate the expression of LZTS2 and induce nuclear export of β-catenin in TNBC.Conclusions: miR-9-5p contributes to β-catenin-activated EMT via downregulating LZTS2, and thus promotes TNBC progression.
The Three Receptor Tyrosine Kinases c-KIT, VEGFR2 and PDGFRα, Closely Spaced at 4q12, Show Increased Protein Expression in Triple-Negative Breast Cancer
